From 73b84bb8224cf54eb4ce8fe6b7b3663198c2b72f Mon Sep 17 00:00:00 2001
From: Barnabas Busa <busa.barnabas@gmail.com>
Date: Wed, 22 Apr 2026 14:00:35 +0200
Subject: [PATCH] miner: supply a slot number when synthesising pending block
 post-Amsterdam

getPending builds the pending block on demand via generateWork, but after
EIP-7843 (#33589) prepareWork rejects the call unless generateParams.slotNum
is non-nil once Amsterdam is active:

    if miner.chainConfig.IsAmsterdam(header.Number, header.Time) {
        if genParams.slotNum == nil {
            return nil, errors.New("no slot number set post-amsterdam")
        }
        header.SlotNumber = genParams.slotNum
    }

getPending never populated slotNum, so on any Amsterdam-activated chain
eth_getBalance(addr, "pending") (and every other RPC that resolves through
the pending state) fails with "pending state is not available", breaking
faucets and nonce trackers that poll pending.

Fix by synthesising a slot number from the parent header when available,
mirroring how the Shanghai branch above already conditionally populates
withdrawals. The pending block is empty post-merge so the exact slot value
is not user-visible; SlotNumber+1 (or zero) is sufficient to satisfy the
prepareWork invariant.

Observed on a bal-devnet-3 Geth build: every eth_getBalance(...,"pending")
returned -32000 "pending state is not available" until the faucet was
repointed at a non-Geth EL. Other clients (Nethermind, Besu, Reth, Erigon,
Ethrex) serve pending on the same chain without issue.
---
 miner/miner.go | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/miner/miner.go b/miner/miner.go
index 0ff0237a08..921200bcaa 100644
--- a/miner/miner.go
+++ b/miner/miner.go
@@ -151,12 +151,24 @@ func (miner *Miner) getPending() *newPayloadResult {
 		return cached
 	}
 	var (
-		timestamp  = uint64(time.Now().Unix())
-		withdrawal types.Withdrawals
+		timestamp   = uint64(time.Now().Unix())
+		childNumber = new(big.Int).Add(header.Number, big.NewInt(1))
+		withdrawal  types.Withdrawals
+		slotNum     *uint64
 	)
-	if miner.chainConfig.IsShanghai(new(big.Int).Add(header.Number, big.NewInt(1)), timestamp) {
+	if miner.chainConfig.IsShanghai(childNumber, timestamp) {
 		withdrawal = []*types.Withdrawal{}
 	}
+	// Post-Amsterdam, prepareWork requires a slot number (EIP-7843). The pending
+	// block is synthetic and has no canonical slot, so derive one from the parent
+	// when available and fall back to zero otherwise.
+	if miner.chainConfig.IsAmsterdam(childNumber, timestamp) {
+		var n uint64
+		if header.SlotNumber != nil {
+			n = *header.SlotNumber + 1
+		}
+		slotNum = &n
+	}
 	ret := miner.generateWork(context.Background(),
 		&generateParams{
 			timestamp:   timestamp,
@@ -166,6 +178,7 @@ func (miner *Miner) getPending() *newPayloadResult {
 			random:      common.Hash{},
 			withdrawals: withdrawal,
 			beaconRoot:  nil,
+			slotNum:     slotNum,
 			noTxs:       false,
 		}, false) // we will never make a witness for a pending block
 	if ret.err != nil {